Copyright Statement

Abstract

Decreasing water availability for rice based systems resulted
in the introduction of water saving production systems such as aerobic
rice and alternate wetting-drying technology. To further improve resource
use efficiency in these systems, water management should be attuned to
critical growth stages, requiring accurate prediction of crop phenology.
Photoperiod-sensitivity of aerobic rice genotypes complicates the
estimation of the parameters characterizing phenological development and
hence impairs predictions. To overcome this complication, we followed a
two-step approach: 1) the photoperiod response was determined in growth
chambers, through a reciprocal transfer experiment with variable day
length, conducted at a fixed temperature, and consecutively, 2) the
temperature response was studied by combining the obtained photoperiod
parameters with data from field experiments. All four aerobic rice
genotypes tested exhibited strong photoperiod-sensitivity. Durations of
basic vegetative phase (BVP) i.e. when plants are still insensitive to
photoperiod, photoperiod-sensitive phase (PSP), and post-PSP (PPP) varied
among genotypes. The temperature response of the genotypes was explored
by combining phenological observations in the reciprocal transfer
experiment with observations in two field experiments. The temperature
range in the field experiments was too narrow to obtain convergence to a
unique set of temperature response parameters, regardless whether a
bilinear or a beta model was used. Sensitivity analysis however provided
clear arguments in support of the recent doubts on the validity of a
commonly used set of cardinal temperatures for rice phenology. Using
standard cardinal temperatures overestimated the rate of development at
temperatures below 31 °C. This finding stresses the need for experiments
on rice phenology under a wider range of temperatures.